The present invention relates to locking means for flexible elements. More particularly, the present invention relates to locking means for a flexible element to be wrapped and secured in cylindrical form. Typical of such elements is a cutting die blanket for use in conjunction with a cylindrical anvil roller in a rotary die cutting apparatus.
Rotary die cutting pertains to the art of cutting a moving workpiece, e.g. a continuously moving web or a sheet of material, without interrupting the movement of the workpiece. In typical application, moving webs or sheets of material, such as cardboard and corrugated paperboard, are passed between a cutting roller and an anvil roller. Cutting elements, known as cutting rules, are mounted on the cutting roller for rotation therewith. The anvil roller is provided with a cylindrical cover, known as a cutting die blanket, which fits around the surface of the anvil roller and effectively increases its diameter by twice the blanket thickness. The axes of rotation of the cutting roller and the anvil roller are parallel and displaced by an amount such that at their points of closest proximity the cutting rules penetrate the surface of the die cutting blanket.
As the cutting rules penetrate the surface of the die cutting blanket, a resistance to the penetration is developed which, for purposes of this application, is called a reaction force. Adjustment of the relative positions of the axes of rotation of the cutting die roller and the anvil roller is made to provide a degree of penetration, and therewith a degree of reaction force, sufficient to insure complete cutting of the moving web of material.
One of the most critical problems confronting developers of cutting die blankets has been the construction of blanket-locking structures that permit their rapid assembly and removal with little effort. One example of a cutting die blanket may be found in U.S. Pat. No. 4,073,207. Although the blanket-locking structure disclosed therein, and similar locking devices, have generally served the purpose, they have not proved entirely satisfactory in that considerable effort is often required in the assembly of the blanket on the die cylinder. Such difficulties can have serious consequences. For example, in the rotary die cutting field the machinery normally operates automatically at relatively high speeds thereby generating vast productivity with relatively small labor requirements. Any long work stopages or additional labor requirements caused for die blanket maintenance can clearly be expensive. It is evident, therefore, that when worn die blankets must be replaced it would be desirable to have a system whereby the worn blanket can be quickly removed and replaced with a fresh blanket using a minimum of time and labor. The present invention fills this need.